HCCI combustion moding state control for fuel economy and seamless transitions

Abstract

A method and system for controlling an engine includes a homogeneous charge compression ignition (HCCI) operating zone boundary module determining a first HCCI operating boundary and a fuel rate module determining a first fuel rate from an operator input. The system also includes a switch module modifying the first HCCI operating boundary to a modified boundary in response to a measured mass airflow, cam positions and the first HCCI operating boundary. The system also includes a combustion control module operating the engine in a spark ignited mode when a second fuel rate request is outside the modified boundary.

1. A method comprising:
 determining a first maximum fuel rate; 
 determining a desired fuel rate from an operator input; 
 modifying the first maximum fuel rate to a second maximum fuel rate in response to a measured mass airflow, a position of a camshaft that actuates at least one of an intake valve and an exhaust valve, and the first maximum fuel rate; and 
 operating an engine in a spark ignited mode when the desired fuel rate is greater than the second maximum fuel rate. 
 
     
     
       2. A method as recited in  claim 1  further comprising operating the engine in an homogeneous charge compression ignition (HCCI) mode when a the desired fuel rate is less than or equal to the second maximum fuel rate. 
     
     
       3. A method as recited in  claim 1  wherein determining the first maximum fuel rate comprises determining the first maximum fuel rate in response to engine speed. 
     
     
       4. A method as recited in  claim 1  wherein modifying comprises modifying the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position. 
     
     
       5. A method as recited in  claim 1  wherein modifying comprises modifying the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position corresponding to a minimum negative valve overlap. 
     
     
       6. A method as recited in  claim 1  wherein modifying comprises modifying the first maximum fuel rate to the second maximum fuel rate in response to a calculated maximum fuel rate determined in response to the measured mass airflow. 
     
     
       7. A method as recited in  claim 1  wherein modifying comprises modifying the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position corresponding to a mechanical saturation. 
     
     
       8. A method as recited in  claim 1  further comprising determining a calculated maximum fueling rate by dividing the measured mass airflow by stoichiometry and wherein modifying comprises modifying the first maximum fuel rate to the second maximum fuel rate in response to the calculated maximum fueling rate. 
     
     
       9. A method of controlling an engine comprising:
 determining a mass airflow for the engine; 
 determining an engine speed; 
 determining a first maximum fueling rate in response to the engine speed; 
 determining a desired fueling rate based on an operator input; 
 determining a position of a camshaft that actuates at least one of an intake valve and an exhaust valve; 
 when the position of the camshaft corresponds to a saturated position, modifying the first maximum fueling rate boundary to a second maximum fueling rate based on the mass airflow; and 
 entering a spark ignition mode when the desired fueling rate is greater than the second maximum fueling rate. 
 
     
     
       10. A method as recited in  claim 9  further comprising operating the engine in an homogeneous charge compression ignition (HCCI) mode when a the desired fueling rate request is less than or equal to the second maximum fueling rate. 
     
     
       11. A method as recited in  claim 9  further comprising determining a calculated fueling rate from the mass airflow and wherein modifying the first fueling rate to the second maximum fueling rate comprises modifying the first fueling rate to the second maximum fueling rate based on the calculated fueling rate. 
     
     
       12. A system comprising:
 an homogeneous charge compression ignition (HCCI) operating zone boundary module determining a first maximum fuel rate; 
 a fuel rate module determining a desired fuel rate from an operator input; 
 a switch module modifying the first maximum fuel rate to a second maximum fuel rate in response to a measured mass airflow, a position of a camshaft that actuates at least one of an intake valve and an exhaust valve, and the first maximum fuel rate; and 
 a combustion control module operating an engine in a spark ignited mode when the desired fuel rate is greater than the second maximum fuel rate. 
 
     
     
       13. A system as recited in  claim 12  wherein the combustion control module operates the engine in an HCCI mode when the desired fuel rate is less than or equal to the second maximum fuel rate. 
     
     
       14. A system as recited in  claim 12  wherein the HCCI operating zone boundary module determines the first maximum fuel rate in response to engine speed. 
     
     
       15. A system as recited in  claim 12  wherein the switch module modifies the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position. 
     
     
       16. A system as recited in  claim 12  wherein the switch module modifies the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position corresponding to a minimum negative valve overlap. 
     
     
       17. A system as recited in  claim 12  wherein the switch module modifies the first maximum fuel rate to the second maximum fuel rate in response to the measured mass airflow. 
     
     
       18. A system as recited in  claim 12  wherein the switch module modifies the first maximum fuel rate to the second maximum fuel rate in response to a relative cam position corresponding to a mechanical saturation. 
     
     
       19. A system as recited in  claim 12  wherein the switch module modifies the first maximum fuel rate to the second maximum fuel rate in response to a calculated maximum fueling rate that is determined by dividing the measured mass airflow by stoichiometry. 
     
     
       20. A system as recited in  claim 12  wherein the engine comprises a direct injection engine.